Small unit construction gas meters

ABSTRACT

THE SPECIFICATION DISCLOSES A MULTICHAMBER GAS METER HAVING GAS FLOW TO AND FROM THE CHAMBERS CONTROLLED BY A SINGLE SLIDE VALVE WHICH EXECUTES AN OSCILLATORY COMBINED ROTATIONAL AND TRANSLATIONAL MOVEMENT. A FURTHER ASPECT OF THE DISCLOSURE ALSO RELATES TO A GAS METER BODY HAVING TWO OPEN CHAMBERS AND FORMED AS A TWO PART MOULDED CONSTRUCTION, THE CHAMBERS BEING CLOSED BY DIAPHRAGMS CLAMPED TO THE BODY BY COVERS DEFINING THE REMAINING CHAMBES OF THE METER. THE TWO PARTS OF THE BODY MAY BE FORMED BY MOULDING USING DIES CONVERGING FROM THREE DIRECTIONS TWO OF WHICH DIRECTIONS ARE COLLINEAR.

United States Patent I 72] Inventor Kenneth Frederick Burrett London.England [21 Appl. No. 749,024 [22] Filed July 31,1968 [45] Patented June28, 1971 [73] Assignee United Gas industries Limited.

London, England. [32] Priority Aug. 1, 1967 [33] Great Britain [31]35357/67 [54] SMALL UNIT CONSTRUCTION GAS METERS 12 Claims, 19 DrawingFigs.

[52] US. Cl 73/268 1 G01! 3/20 [50] Field of Search 73/268, 267, 263,264, 248, 249, 250; 91/178, 218, 325

[56] References Cited UNITED STATES PATENTS 1,246,613 12/1917 Knight73/267 3,161,049 12/1964 St. Clair 73/267 FOREIGN PATENTS 810,022 6/1954Great Britain 73/268 Primary Examiner-Richard C. Queisser AssistantExaminer-Ellis .I. Kock Attorney-Cushman, Darby & Cushman ABSTRACT: Thespecification discloses a multichamber gas meter having gas flow to andfrom the chambers controlled by a single slide valve which executes anoscillatory combined rotational and translational movement. A furtheraspect of the disclosure also relates to a gas meter body having twoopen chambers and formed as a two part moulded construction, thechambers being closed by diaphragms clamped to the body by coversdefining the remaining chambers of the meter. The two parts of the bodymay be formed by moulding using dies converging from three directions,two of which directions are collinear.

PATENTEU JUN28 I971 SHEET 1 [1F 9 PATENTEU JUN28 I97! I 8587.315

sum 2 OF 9 A llorney 5 v WZMM 4, 97141;

Atlorney 5 PATENTEU JUN 2 8 IQYI SHEET u UF 9 Inuenlor Ai /mar FBVRflf/TB 2 MM. 1%%Y Attorney 5 PATENTED JUN28 I971 3,587,315 sum 5 OF 9Attorney pmrzmm mam 3587.315

SHEET 8 OF 9 ALF- 64 -Z WZMM y??? Allorney;

PATENTED JUN28|97I 3587.315

sum 9 or 9 SMALL UNlT CONSTRUCTION GAS METERS The present inventionrelates to an improved dry gas meter.

It is an object of the present invention to provide a dry gas meter ofthe movable wall construction and which has an improved efficiency dueto a reduction in valve drag with respect to the drag of a conventionalrotary valve.

Conventional dry gas meters employ a pair of valves each cooperatingwith three valve ports opening into a gas inlet chamber. The three portsassociated with each valve communicate with a pair of adjacent gasmeasuring chambers separated by one or more diaphragms, and an exhaustport to which each of the first two ports is selectively communicated bymeans of the associated valve. The valve construction must be such thatat no time is the exhaust port exposed to the gas inlet chamber. Sincetwo valves are used in the meter it follows that the valve drag andinertia of each valve and its associated linkage is duplicated.

According to one aspect of the present invention there is provided amovable wall gas meter including a single valve adapted to prevent atall times direct gas flow between inlet and exhaust, and arranged toexecute a cycle in which each of the chamber ports of the meter iscommunicated to inlet for part of the cycle, to outlet for a furtherpart of the cycle, and is sealed with respect to inlet, outlet and allother chamber ports, during the remainder of each cycle, said valvecomprising a valve slide member which executes simultaneouslyoscillatory motion in both the rotational and translational modes in thesame plane.

In one form of apparatus of the invention, the valve member comprises adomelike chamber having a peripheral seating portion, and the chamberports are defined in a valve seating member over which the valve slidemember slides. Preferably, the index drive shaft of the meter isconnected to the valve slide member at a location which executes merelya circular motion about the axis of the index drive shaft, duringoperation of the valve slide member. Desirably, the inner and outeredges of the sliding surfaces of the valve are so shaped that, onceduring a cycle of operation of the valve, parts of each edge of thesliding surface of the valve slide member are in turn substantiallycoincident with and parallel to parts of the edges of associated ones ofthe chamber ports. in a four chamber meter the chamber ports may bearranged in pairs so that when one port of a pair is open to inlet theother port of the same pair is in communication with exhaust and duringthis time the ports of the other pair are closed to both inlet andexhaust.

Suitably a meter body including four chambers and the ductscommunicating the chambers with their respective chamber ports of thevalve is placed within a casing, the space within the casing andsurrounding the body being exposed to measured exhausting gas and theindex drive gear box being disposed within said space directly below thevalve slide member and the chamber ports may be distributed around acentrally disposed exhaust port and wherein the inlet chamber of themeter is situated on one side of the valve assembly and the exhaustchamber is situated on the other side of the valve. Advantageously saidvalve is mounted above a top wall of said casing and is disposed withina top cover which is secured to said casing, the space beneath said topcover being exposed to inlet gas entering the meter and being sealedwith respect to the space within said casing by means of the valve, anexhaust duct extending through the space within said top cover andcommunicating the space within said casing and a conduit discharging gasfrom said meter, said duct being associated with a shutoff valve forarresting flow of exhausting gas. The valve ports may be so arrangedthat the combination of the exhaust port and one pair of mutuallyopposite chamber ports, when taken together, forms a trapezium, and thecombination of the exhaust port and the other pair of mutually oppositeports taken together forms a rectangle.

Conveniently at least, one top arm of the meter is connected directly tothe valve slide member, and the other arm may be arranged to drive theindex drive shaft by means of suitably disposed links. in such a caseone flag rod of the meter extends sealingly through said top wall of thecasing and is provided with a top arm which is pivotally connected tothe valve slide, the other flag rod of the meter terminating within thespace bounded by said casing and being connected to a crank extendingtransversely of the lower end of a vertically disposed index driveshaft, by means of a suitable linkage, the underside of said valve slidebeing provided with a peg which engages with a crank extendingtransversely from the top end of said index drive shaft. Alternativelythe index drive shaft may be driven by the top arms of the meter and maytransmit motion to said location on the valve slide member.

A separate aspect of the invention provides a four chamber meter havinga central body which contains two gas measuring chambers and all theducting between at least some of the chambers and valve ports, the bodycomprising two separately formed moulded components, the other twochambers of the meter being provided by covers sealingly fastened to themeter body, said other chambers being separated from the first twochambers by the diaphragms of the meter. Conveniently, a top case of themeter may be sealingly joined to the top of said central body, andenclose the valve gear of the meter, there being no bottom case fittedto the meter. Preferably, each diaphragm is clamped between a face ofthe body and an adjacent face of one of said covers. Desirably, said twomoulded components are formed of a synthetic plastics material, e.g.,DELRIN. Conveniently, the bonding of the two components may be performedby ultrasonic welding. Alternatively, the meter body components may beformed of conventional materials such as phenolic resins and may besecured together by bolts, the joints being sealed either with gasketsor adhesives. Each of said chamber defining covers may be fastened tothe main meter body by means ofa flange on said cover engaging with aflange on said body, means being provided for holding said two flangesin engagement. Conveniently, the flanges may be held in engagement bymeans of clips, each clip being of a U-shape and comprising a bridgeportion between a pair of limbs converging towards their free ends, saidflanges being provided with locations at which the nonadjacent surfacesof the flanges, when assembled, have cross sections convergent away fromthe edges of the flanges. An alternative form of union between the twoflanges comprises adhesively securing the flanges. Advantagcously, thecovers are made of a synthetic plastics material similar to that of themain meter body, and the covers are secured to the body by means ofultrasonic welding.

Advantageously the meter body, when assembled, has the ductingcommunicating the valve ports with the gas measuring chambers formed inits upper part, and has a pair of chamber defining shells extending fromits lower part, each shell having a flange around its periphery and thetwo shells of a pair being disposed in back-toback relation.Conveniently, the outer surface of each chamber defining shell isprovided with a projecting rib, each shell being formed in one of themoulded parts of the meter body and said ribs being so dimensioned that,when the two parts of the meter body are joined together, the rib of oneshell engages with and is weldable to the rib of the other shell.

Conveniently, each meter body moulding includes a portion of the ductingwhich extends vertically through the body portion and provides anaperture allowing through passage of the associated flag rod.

Desirably also the exhaust port comprises one end of the arm of aU-shaped passage formed in the central body, the other end of thepassage communicating with an exhaust duct to convey the measured gasesaway from the meter.

The invention further provides a method of forming a gas meter bodyportion comprising separately moulding a pair of components containingducting adapted to communicate the meter gas measuring chambers to theassociated valve ports, each moulding operation being carried out bymeans of converging die parts from three directions two of whichdirections are directly opposed to one another along the same straightline, said two moulded components then being bonded together to form asingle meter central body portion.

In order that the various aspects of the present invention may morefully be understood, the following description is given, merely by wayof example, reference being made to the accompanying drawings, in which:

FIG. II is a top plan view, partly in section, ofa dry gas meterillustrating certain aspects of the present invention;

FIG. 2 is a side elevational view, again partly in section, of theapparatus of FIG. 1;

FIG. 3A is a diagrammatic view of the valve grid of the meter of FIGS. 1and 2;

FIGS. 38 and 3C are underneath plan views of alternative constructionsfor the valve slide;

FIGS. 4, 5, 6 and 7 are schematic views illustrating the relationshipbetween the valve slide and valve grid in each of four positions duringthe movement of the valve slide;

FIG. 8 is a top plan view of the meter of FIG. 1 but with the index, toparms, valve gear and pan covers removed;

FIG. 9 is a sectional view taken on the line IX-IX of FIG. 8;

FIG. 10 is a sectional view taken on the line X-X of FIG. 8;

FIG. 11 is a side elevational view showing the apparatus of FIG. 8 whenviewed along the direction of the arrow XI thereof;

FIG. 12 is a perspective, exploded view showing an alternative form ofvalve slide and driving arrangement;

FIG. 13 is a top plan view ofa further form of valve grid;

FIG. 14 is a top plan view of a valve slide for use with the grid ofFIG. 13;

FIG. 15 is a top plan view of a further embodiment of meter according tothis invention;

FIG. 16 is a side view of the meter body of FIG. 15, shown partly insection and with the outline of the meter casing shown in full lines;and

FIG. 17 is a top plan view of the meter body shown in FIGS. 15 and 16,but with the valve mechanism removed.

Referring now to the drawings, and more particularly to FIGS. 1 and 2,the dry gas meter 1 is of the form comprising four chambers arranged inpairs, each pair of chambers being separated by a diaphragm. The mainbody 2 of the meter has a pair of pans 3 and 4 clamped one to each side,the pans 3 and 4 forming the housings of the outer chambers of themeter. The top of the meter is closed by a valve plate 5 having anexhaust duct aperture 6 formed therein. Selective filling and exhaustingof the various chambers of the meter is performed by means of a slidevalve comprising a slide 7 cooperating with a valve grid 8 formed in thevalve plate 5. The valve drive mechanism in this apparatus is of theconventional form comprising flag rods 9 and 10 which are rotatablydriven by flag arms connected to the diaphragms of the meter. Anoutwardly extending arm 11 of the valve slide 7 has a slot 12 throughwhich an upstanding pin 13 of the valve plate 5 projects. Thus, thevalve slide is permitted pivoting movement about the pin 13, and alsosliding movement of the arm 11 longitudinally of itself within thelimits defined by the ends of the slot 12 which engage pivot pin 13.

Particular reference to FIG. 2 will reveal the method by which the valveslide is driven from the flag rods. The flag rods 9 and 10 have top armsM and 15 respectively extending upwardly and radially outwardlytherefrom. Tangent arms 16 and 17 (represented in FIG. 1 by means ofdot-dash lines) are pivotally attached to the free ends of top arms Mand 15, and are pivotally linked together on a crank pin 18 extendingupwardly from a crank arm 19 on the upper end of the index drive shah orcrank spindle 20. Tangent arm 16 joins top arm 14 to crank pin 18, andtangent arm ll7join top arm 15 to the crank pin. The index takeoff gearhousing 21 is supported by means not shown, and thus the index driveshaft is constrained against lateral movement, and is merely permittedrotational movement about its own axis. The lower end of the index driveshaft 20 is provided with a further crank 22 which has a downwardlyextending crank pin 23 attached to the free end thereof. This crank pin23 is freely rotatably mounted in a recess 24 in the top surface of thevalve slide 7 and thus the recess 24, by virtue of the constraint of theindex drive shaft 20, is permitted a circular motion about the axis ofthe index drive shaft 20.

It will be seen, from a study of the pattern of movement of the valveslide 7, that in effect the slide executes a pattern of rotary motionsimilar to that followed by a conventional radial gas meter valve butthat the movement is a compound of two oscillatory motions each onebeing based on one of a pair of orthogonal axes. Thus while the valveslide 7 executes a radial motion about the fixed pivot pin 13 the effectof the slot 12 slidable past the pivot pin 13 is similar to that ofproviding a radial motion symmetrical about an axis perpendicular to theaxis of the motion about pin 13, namely perpendicular to thelongitudinal axis of the arm 11 as viewed in FIG. 1. Clearly, suchmotion may take place in several different forms and, in

the embodiment of FIGS. 1 and 2, the only constraint on this motion isthat the recess 24 executes a continuous, purely circular motion aboutthe axis of the index drive shaft 20. It will no doubt be appreciatedthat, due to the complex motion of the valve slide 7, the motionexecuted by every other individual point on the slide 7 will becontinuous but will not necessarily be circular, and in fact will almostinvariably be other than circular (e.g., elliptical).

The index drive takeoff gearing comprises a worm gear 25 fixed to theindex drive shaft 20 and cooperating with a pinion 26 fixed on the indexspindle 27.

The space above the valve plate 5 of FIGS. 1 and 2 will be enclosedwithin a gastight casing which is not shown, this casing forming theinlet chamber of the meter. The exhaust aperture 6 is provided with anupwardly extending exhaust duct 28 (see FIG. 2) which will extendsealingly through the abovementioned casing and communicate with the gasconduit leading to the distribution network, for example domestic gaspiping and equipment. An inlet aperture in the nonillustrated casingwill provide a mounting for the inlet duct of the meter, i.e., the gasmain.

Since the drive arrangement of the flag rods 9 and 10 is ofaconventional form, no detailed description is given hereinafter of thedriving of these arms, but it will be understood that rotation of thecrank pin 18 about the axis of the index drive shaft will follow fromthe oscillatory pivoting movement of the top arms 14 and 15 whichresults from movement of the diaphragms of the meter. Thus, the crankpin 23 is driven for rotation about the axis of index drive shaft 20 andthe recess 24 in the top surface of valve slide 7 is caused to perform asimilar circular motion.

During rotation of the crank pin 23, the circular motion of recess 24will cause oscillatory pivotal movement of the valve slide 7 about pin13, together with reciprocatory motion of the slide along the directionof the slot 12. This motion of the valve slide 7 will cause opening andclosing of selective valve ports which are defined within the valve grid8. As explained above, the inlet gas to the meter is contained within atop cover which is not shown and the gas enters through the valve grid 8to the measuring chambers. In this particular construction of dry gasmeter the four measuring chambers each have an inlet port defined in thevalve grid 8, and a further port at the grid conveys the exhaust gasthrough a duct communicating with the exhaust aperture 6 and exhaustduct 23.

The four measuring chambers of the meter are formed as follows. The pan3, which is clamped to the main block 2 by means of spring clips 29holding together the flanges 30 and 31 on the pan and blockrespectively, encloses a first measuring chamber denoted by the letter Ain the drawing. Two further chambers B and D are defined within thelower part of the meter block 2 but are separated from each other by awall formed within the block. The chamber B is uppermost as viewed inFIG. 1. Finally, a chamber C is defined within the pan 4 which is heldonto the block 2 by means of further spring clips .32 clamping flanges33 and 34 together. The chambers A and B are separated from one anotherby a diaphragm which is clamped between the two flanges 30 and 31, andsimilarly the chambers C and D are separated by a further diaphragmclamped between flanges 33 and 34.

In order more clearly to illustrate the functioning of the valve slide 7and grid 3, FIGS. 3A and 38 respectively, show somewhat diagrammaticrepresentations of the valve grid 3 and the valve slide 7. FIG. 3A showsthe general outline of the valve grid 8 shown in dotted lines, and thefive ports shown in full lines. A and 8 denote two rectangular chamberports and C and D denote two trapezoidal chamber ports, these referenceletters being used to denote the connections between the chamber portsand the respective measuring chambers i.e., chamber A is associated withport A etc. The central trapezoidal port labeled E in FIG. 3A is theexhaust port which, as explained above, communicates with the exhaustduct 28. FIG. 3A also shows the fixed pin I3 which guides the motion ofthe valve slide 7 so as to induce limited rotational movement in theplane of the valve seating surface.

Turning now to FIG. 38, there is shown one rather simplified form of thevalve slide 7, showing the slide consisting of a longitudinallyprojecting arm Ill and a head 35, the head having a central aperture 36formed therein. A slot 12 is formed at the free end of arm II, asillustrated in FIG. I. It should be pointed out that the view of FIG. 38corresponds to an underneath plan view of the valve slide, therectangular recess as comprising a domelike chamber which forms atransfer port for allowing the measured gas returning from each chamberto be transferred across into the centrally disposed exhaust port E. Inthis FIG., the area of head portion 35 surrounding the recess 36constitutes the flat underneath face of the valve slide 7, this facesealingly cooperating with the valve grid 3.

The view of FIG. 3C, in which like reference numerals have been used fordenoting like parts to those of FIG. 3B, shows an alternative form ofvalve slide 7 in which the head portion 35 and in particular the recess36 has a different shape to that of FIG. 38. Neither the head 35 nor therecess 36 now have rectangular walls, but instead the head 35 has theform of an irregular lO-sided polygon, and the recess 36 has the form ofan irregular hexagon. The general dimensions of the two valve slidesillustrated are substantially the same, i.e., the length of slot I2 isequal, the distance between the midpoint of slot I2 and the center ofrecess 36 is equal and the overall dimensions of the head portion 35 andrecess 36 are similar, and in fact these two valve slides 7 are designedfor use with the same valve grid. However, clearly the variation of theshapes of the components of the valve slide 7 of FIG. 3C has enabled aconsiderable reduction in the amount of material required, and hence hasprovided a valve slide of lighter weight and consequently of lowermoments of inertia about the center of slot 12 and about the center ofrecess 36.

It will of course be appreciated that if the outer periphery of thevalve slide 7 is unnecessarily large, then although each of the outerports A, B, C and D will be adequately sealed with respect to the inletspace during at least three-fourths of the cycle of the valve slide 7,during the remaining period of the cycle of the slide 7 the degree ofexposure of the individual port to the inlet space during an inletstroke will be insufficient. In the extreme, a very large valve slide 7will never open any of the outer ports to inlet and the meter will notfunction.

It is therefore important that, as described below with reference toFIGS. 4, 5, 6 and 7, the outer periphery of the seating surface of thevalve slide 7 should be as small as possible consistent with therequirement for sealing each of the ports from the inlet space at alltimes other than an inlet cycle involving the particular port concerned.

Such reduction in size of the valve slide 7 of FIG. 3C has beenaccomplished by arranging that the outer periphery of the head is assmall as possible while still ensuring that each port is opened to theinlet chamber only once during each revolution of the index drive shaft20. This involves arranging each outer edge of the sealing face of thevalve slide 7 so that when that edge is sealing off a port to the inletchamber but opening it for transfer to the exhaust port it issubstantially coincident with the edge of the port in questionfurtherest from the exhaust port. Similarly, the increase in area of thedomelike chamber is achieved by ensuring that when a particular port issealed with respect both to the inlet chamber and to the exhaust port,then the edge of the port nearest the exhaust port is substantiallycoincident with the nearest edge wall of the domelike chamber.

FIGS. 8 to 7 show the valve slide 7 in dotted lines superimposed on thevalve grid 8 of FIG. 3A in each of the four principal positions of thevalve slide during rotation of the crank pin 23 about the axis of indexdrive shaft 20. The index drive shaft 20 and the recess 24 which isformed in the top surface of the valve slide 7 are both illustrated indotted lines in FIGS. 4 to 7 in order toillustrate the rotational motionof the crank pin 23 and recess 24 about the axis of the shaft 20.

Also in FIGS. 4 to 7, diagonal crosshatching has been used to denote theport area open to inlet, and vertical crosshatching denotes the area ofexhaust port E and the respective port connected for transfer of gasesthereto.

FIG. 4 shows the position in which port A is open to transfer measuredgas to the exhaust port E, and the port B is open to the inlet chamber.Thus, the gas to be measured passes downwardly through the diagonallycrosshatched area of port B, into chamber B, and in so doing urges thediaphragm dividing chambers A and B to move towards chamber A so as toreduce the volume of chamber A. At the same time the already measuredgas in chamber A is expelled by this movement of the diaphragm andpasses up through port A and is transferred, via the domelike chamber365, down into the exhaust port E.

After a quarter of a revolution of the crank pin 23 about shaft 20 tothe FIG. 5 configuration the valve slide 7 is in a position where port Dis open to inlet and port C is transferring to exhaust. Here again theinflowiing gases through port D cause movement of the dividing diaphragmbetween chambers C and D so as to expel the already measured gas inchamber C and cause it to pass out through port C and be transferred tothe exhaust port E.

A further quarter of a revolution of the crank pin 23, will result inthe position shown in FIG. 6, in which port A is open to inlet and thegas in chamber B is thusexpelled through port B to exhaust. Finally, inFIG. 7, port C is open to inlet and port D is discharging to exhaust.

Reference to FIGS. 4% and 6 will show that in one case (FIG. 4) theportion p of the outer periphery of the valve slide 7 is substantiallycoincident with the corresponding portion p of the port D. Similarly, inthe other case (FIG. 6) the portion q of the periphery of the valveslide 7 is substantially coincident with the corresponding portion q' ofthe port B. The result of this characteristic is that, as shown in FIG.5, during the inlet cycle involving port D, the port I) is substantiallycompletely exposed to inlet but is nevertheless sealed with respect bothto the exhaust port E and to each of the adjacent chamber ports A and B.A similar situation exists with regard to each of the other ports andwith regard to each other portion of the periphery of the valve slide 7.

The above description of the movement of the valve slide 7 is somewhatsimplified, since there will be a tendency for the two diaphragms to beat their extremes of movement at the same time. It is thereforenecessary to stagger the operation of the diaphragms so that when one isat an extremity of its movement the other is still approaching oralready departing from its midstroke position. As is well known in theconstruction of dry gas meters, some form of timing adjustment hasnormally to be incorporated, this adjustment being possible for exampleby traversing the pin 13 across the valve plate in a directiontransverse to the particular orientation of arm II in FIG. 7. In thismanner it can ensured that while one diaphragm is at an extremity ofmovement the position of the other one, which is approaching ordeparting from its respective midpoint is adjustable in order that thesetting may be chosen to be appropriate for the meter to function in acontinuous manner. Clearly, once the correct timing setting has beenfound it will be possible either to clamp the pin 13 in the appropriateposition, or to construct all similar gas meters with the pins 13integrally formed with the plate but fixed in the appropriate position.The efficiency of such an integral pin form of meter will depend uponthe degree of accuracy of the manufacture of the flag rods and arms, thetop arms, the valve slide and the valve plate.

FIGS. 8 to 11 provide illustrations of the main block 2 of the meter.The block 2 is formed of a pair of components 36 and 37 which areseparately formed, such as by moulding, but which may be joined by anysuitable manner. Advantageously, the block parts 36 and 37 are formed ofa synthetic plastics material such as that commonly known as Delrin" inwhich case a particularly suitable method of joining the two block partstogether comprises ultrasonic welding to join the two components 36 and37. However, the block parts could be made of phenolic resin and boltedtogether, a sealant such as adhesive or a gasket being applied to thejoint. The top plan view of FIG. 8 shows the block 2 when the valveplate 5 and all the valve gear, flag rods and index drive have beenremoved. In order to illustrate the connection between the valve portsA, B, C and D and the respective chambers A, B, C and D the ductingformed in the block has been given similar referencing A", B, C" and D.Similarly, the exhaust passage which communicates exhaust port E withthe exhaust duct 2% has been reference E in this view.

FIG. 8 shows clearly that ducting A" communicates, by means of a ductingportion 40', with chamber A which would be formed when the pan 3 and itsdiaphragm are placed in position. Similarly, ducting B" is shown tocommunicate between the approximate position of port B (i.e., to theleft of exhaust passage E in FlG. 8) and the chamber B formed in theblock portion 36. This is by means of a ducting portion 41 which passesdownwardly into the block 2 and thence back under the ducting D" andinto chamber B. The construction of this ducting portion 41' is shownclearly with reference also to FIG. 9. The ducting C is shown in FIG. 8to communicate between the approximate position of port C and thechamber C, via a ducting port 412. For understanding of the constructionof ducting D", reference must be made to both FIGS. 8 and 9 where it canbe seen, from the approximate position of the port D, that a ductingpart 43' passes downwardly into the chamber D illustrated in FIG. 9.Finally, the exhaust passage E passes downwardly under the ducting C"and up to a location adjacent the approximate position of exhaustaperture 6 in the valve plate 5.

The configuration of the various ducting parts is best appreciated withreference to the sectional view of FlG. 9 taken on the line lX-IX ofFIG. 8, and to the sectional view of FIG. w taken on the line X-X ofFlG. 8.

The sectional view of FlG. l0 and the side elevational view of FIG. 1!illustrate, between them, the chamber 8 defined within the block part36. FlG. l 1 shows a view looking into the chamber and FlG. 10 shows theview as seen from the opposite direction looking towards the outer faceof the chamber in the form a shell-like structure formed in the bottompart of block portion 36. in FIG. 10, a projecting rib 38 is shownformed in the rear face of the block part 36, this rib 38 being weldedto a similarly formed corresponding rib on block part 37. The welding ofthe two ribs gives a stronger construction and reinforces thecombination of the two measuring chambers B and D.

The clips 29 of FIG. 11 are adapted to engage in suitably formedlocations 39 of FIG. 10 and, as can be seen in H6. 1, the clips 29 areeach of U-shape, having a bridge portion joining a pair of limbsconverging towards their free ends. The clip locations 39 are formedwith a slight reentrant angle, i.e., the cross section of the flanges 30and 31 at a clip location 39 is such that the thickness at the edge ofthe flange is greater than the thickness inboard of the edge. Thus, theclips 29 are prevented from inadvertent release from the flanges and asecure joint is achieved. Alternatively, the pans 3 and 4 may befastened to the block 2 by means of adhesive, welding, or any othersuitable joining process.

In the meter illustrated, in which the two flanges are held together byan external clip, the diaphragms of the meter are held between each pairof engaging flanges 30, 3!. or 33, 34. By pressing the two flanges of apair firmly into engagement, with the diaphragm clamped therebetween,the assembly provides a pair ofgastight measuring chambers separated bya single diaphragm.

The diaphragm may be of genuine leather, or any suitable plasticsmaterial which is able to withstand the corrosive constituents of thegas being measured. This construction of the meter block 2 isparticularly advantageous since the provision of the pair of ribs 38which may be welded together and which may fonn a spacer between the twochambers enables the considerable reduction to be achieved in thequantity of material used for moulding the block. Known meters of theblock type construction have the chambers formed entirely within theblock, rather than having ducting arranged within a block and then thechambers formed as shells projecting from the block. The strength of theshell construction described is clearly improved by the presence of thetwo welded ribs 38.

Furthermore, the crossover" configuration of the ducting in the blockenables the drive to the valve slide to comprise a single-throw crankwhereas, with a more conventional layout of ducting, i.e., where port Ais adjacent port B instead of being diametrically opposite to it, adouble-throw crank arrangement would be required in order to maintainthe correct sequence of operation of the meter. As can be seen clearlyfrom FIGS. 8 to 11, the particular construction of the two-part meterblock used enables the various ducts to be formed in the mouldingrelatively simply and cheaply. Clearly, the various parts of theducting, although separated by walls formed in the mouldings 36 and 37,are only gastightly separated from each other when the valve plate 5 isin position. Thus, it is important that suitable sealing means beincluded between the top face of the block 2 and the lower face of thevalve plate 5 in order to seal the various parts of the ducting withrespect to each other.

The side elevational view of FIG. 11 shows the opening of the ducting B"into the chamber B, andalso shows the opening of ducting part 40' ofducting A conveying the gas to and from chamber A when the pan 3 anddiaphragm are in place.

Although not specifically illustrated in the accompanying drawings oneof the two flag arms would be positioned within chamber A, and will haveone end pivotally attached to the diaphragm separating the chambers Aand B. The other end of the arm will be fixed to the lower end of theassociated flag rod 10 which will be situated within the vertical partof ducting A". The opening of the ducting part 40 which is visible inFIG. Illl therefore provides the location for the lower end of flag rod10 and the associated flag arm. From its lower end the flag arm 10 willextend upwardly through the vertical part of ducting portion 40' (asviewed in plan in FIG. 8) and will then pass through the valve plate 5via a suitable stuffing box or other sealing device. The location offlag rod 9 with associated flag arm on the meter block component 37 willbe substantially the same as the arrangement just described.

As described above it is possible for the pans 3 and 4 to be attached tothe meter block 2 by means of adhesives or welding. Where a weld forexample an ultrasonic welding joint has been used, there will be nodanger of tampering with the meter and possibly removing either of thepans 3 and 4 and thus there will be no requirement for a bottom case tobe provided for the meter. In this form of meter it will be possible forthe valve plate 5 to be extended laterally slightly and for the topcover of the meter (not shown in the accompanying drawings) to befastened to the valve plate with a gastight seal between these twocomponents. Thus the construction of the meter will be considerablysimplified since there will now no longer be a requirement to provide abottom case component which hitherto had to be provided inter alia toprevent tampering the the pan cover joints and possible leakage of themeasuring chambers thereby.

A further, more preferable form of valve slide is shown at 7 in FIG. 12.This FlG. is a perspective exploded view showing a valve grid 8 similarto that described with reference to FIGS. 4, 5, 6 and 7. In thisparticular form of meter however, the tangent cranks have beeneliminated from the apparatus and the top arms 14 and 15 are connecteddirectly to the valve slide 7'.

The valve slide 7 has a pair of mutually perpendicular arms 40 and ithaving a slot 42 and hole M respectively at their free ends. Top arm 14'has an upwardly extending pivot pin 4d at its free end, such pin Mengaging in the hole 43 at the end of arm 41. A similar pivot pin d5 isprovided at the free end of top arm 35 and engages in the slot d2 of armd0. Once again the index drive shaft 20 has a crank 22 at its lower end,and is restrained against lateral movement by means of the mounting ofthe index takeoff gear casing 211. However, in this embodiment the crank22 has an aperture lb which freely rotatably receives a pin 47integrally formed on the upper face of the valve 7 In this manner thepin 47 is only permitted rotational movement along a circular orbitcentered on the axis of index drive shaft 2b. In other words, theassembly of top arms M and 15 together with the valve slide 7' hasreplaced the linkage lld, i5, M, 17, lb and I9 of the constructionillustrated in FlGS. ii and 2.. The two top arms M and 15 are againfixed to the upper ends of their respective flag rods 9 and lid as canbe seen from MG. 112. During operation of the meter, each top arm isfree to rotate through a small angular distance such that the respectivepivot pin dd or 15 is allowed to move between two positions separated bya distance denoted 2R in FIG. H2. The radius of the orbit of pin 47about index drive shaft 20 (Le, the spacing between index drive shaft 20and aperture as of crank 22) is equal to the distance R, and the slot 42has a length again equal to 2R.

As top arm 15 rotates about the axis of its associated flag rod the pin45 moves backwards and forwards along a path 2R in length. This causespivoting of the valve slide 7 about hole 43, together with a certainamount of movement of pin 45 longitudinally of slot 412. Similarlyrotation of top arm M about the flag rod 9 causes pin 44 to move along apath ER in length, this in turn moving the hole 43 along a similar path,causing pin 35 to traverse a slot 42. The particular configuration ofthe valve slide 7', the flag rods 9 and w and the top arms M andprovides for substantially a purely rotational movement of the pin 47 tobe produced. However, due to the constraint of index drive shaft and thefixed radius of crank 22 this motion can only be a purely circularorbiting movement, and thereby will result in rotation of the indexdrive shaft 20 and of the index itself. During such rotational motionthe various ports of the valve grid d are communicated to inlet and totransfer with exhaust, thereby maintaining the ap propriate diaphragmmovement necessary for rotation of the flag rods.

The double-radial" motion described above with reference to FlGS. 3a,3b, and 30, can more clearly be seen to be followed in the embodiment ofFIG. 12. The oscillation of top arm 15 about flag rod it) would causethe valve slide 7' to execute a radial movement about pivot pin 44 onthe other top arm 14. However, the pin 44 is itself moving, due to theoscillatory pivotal motion of the second top arm lid about flag rod 9,and is also giving rise to a radial" oscillating movement of the valveslide 7 about pivot pin d5 on the first top arm 15.

Although the valve grid and valve slides disclosed in the foregoingdescription have been so shaped that the valve grid is of relativelysimple form and the valve slide of relatively complex form with theadvantage that the material used for the valve slide is substantiallyreduced, it is possible for the valve grid to be of complexconstruction, and for the valve slide to be relatively simple. Thus,instead of each port A, B, C, D and E being of quadrilateralconstruction it is envisaged that the various ports should consist ofirregular polygons having more than four sides.

H6. 113 illustrates, in plan, an alternative form of valve grid 8", andFIG. M shows a top plan view of the valve slide 7" suitable for use withthe grid d. The configurations of the grid and slide illustrated inthese FIGS. have been arrived at by a process similar to that describedabove with reference to FIGS. 3a, 3b and 3c.

The reference numeral 48 denotes blind ports which are provided so thatthe outer periphery of the valve grid ti" encloses a sufficiently largearea to ensure that at no time during the movement of the slide 7"between its four principal positions is the exhaust port F communicatedto the inlet chamber. The grid 8 can be seen as comprising a pluralityof upstanding walls d9 enclosing a central port area E, the four portsA, B, C and D and the four blind ports 38. The crosshatched areas of theports A, B, C, D and E represent the apertures in the valve plate 5.

H61. shows a top plan view of yet a further embodiment of slide valveaccording to the present invention. It can be seen that one top arm 15"is connected to the valve slide 7 by means ofa pivot pin $5 on the freeend of the top arm I5 and engaging in a suitable aperture at the end ofan arm 30" of the valve slide.

This particular embodiment of meter is shown in side elevational partlysectional view in FIG. 16 in which part of the meter is shown as a puresection taken down the center of the device and the remainder is shownas an elevational view of the meter body disposed within the outercasing which is shown in outline only.

FIG. 17 illustrates a top plan view of the parts of the meter remainingafter the valve seating member 50 and top cover 53 of the meter havebeen removed, leaving the gear box 52 exposed. From FIGS. lb and I7 itcan be seen that the other top arm 14 of the meter is disposed at thesame end of the meter as top arm 15" shown in FIG. 15 and :is connectedby a link 53, to a crank 54 fixed to and extending transversely of theindex drive shaft 55.

As shown clearly in FIG. 16, the top end of the index drive shaft 55 islocated directly under the valve slide 7 and is provided with atransversely extending crank 56 having a hole near its free end throughwhich extends a pin 57 formed integrally with and extending downwardlyfrom the valve slide 7". Thus, during rotation of the index drive shaft$5, the valve slide 7" will be caused to execute a motion in which thepin 57 moves in a circular orbit around the axis of drive shaft 55.

Clearly, although the two top arms id" and 16" have their upper ends atdifferent levels within the device, the linkage comprising link 53,crank 54, index drive shaft 55, crank 56, pin 57 and arm Ml provides adirect mechanical connection between the two top arms 14" and 3.5". Byappropriate arrangement of the crank angles between the variouscomponents of this linkage the meter may be constructed to have adesired timing setting and to operate continuously during passage of gastherethrough. Although the device of FIGS. 15, i6 and 117 only has onepoint of direct attachment to a top arm, namely pin 45$" on arm as", themotion is nevertheless constrained to be identical to that executed bythe embodi ment of FIG. 32 since the top arm 15" executes an oscillatingmotion about the associated flag rod 1d" and the pin 57 of valve slide7" executes a clearly rotary motion about the axis of the index driveshaft 55, similar to the motion of pin 47 about the axis of index driveshaft 20 in FIG. 112. Thus, here again a double-radial type of movementensues.

Although the embodiment of H68. 15, i6 and R7 has a slightly differentducting arrangement to that described in detail above with reference toFIGS. to ill, it will be appreciated that the principle of operation isthe same and that therefore no detailed description of the chamberconstruction is required, in order to explain the action of the slidevalve 7". It should be understood that the valve seating member 5t)communicates each of the valve ducts A, B, C and 1D with the relevantports of the valve base, the exhaust passage being formed by the spaceconfined within the top cover 51 and the bottom cover 5% comprising thecasing of the meter. Exhaust gas from the meter passes upwardly out ofthis space through a prepayment shutoff valve of housing 59 once theprepayment shutoff valve flap bit has been pivoted in the clockwisesense about its pivot pin til. The inlet chamber of the meter isconfined within a suitable outer top cover (not shown) which will besealingly fastened above the top cover 51, and an exhaust stack (notshown) extends upwardly from the prepayment shutoff valve housing 59through the outer top cover in order to convey the measured gas away toone or more appliances.

The construction of gas meter illustrated in FIGS. l5, l6 and 27 isconsiderably smaller than the conventional meter having the same sweptvolume, since the index gear box 52 has now been placed below the valvemechanism of the meter, within the exhaust space confined by the outercasing 511 and Furthermore, the two flag rods 9 and E0" of the meterhave now been placed at the same end of the meter rather than beingdiagonally oppositely placed as shown in the embodiment of H68. 1 to H2,and thus the field of movement of the top arms and associated linkagehas been considerably reduced with respect to the conventional meter.Clearly, by placing the flag rods 9" and It)" so close together it hasbeen made possible to reduce the depth of the meter (the vertical extentas viewed in FIGS. and 17).

It has been found that the power index factor for the meter valve can bemaintained at just below the value of 1.2. The calculation to determinethe power index factor is specified in British Standards No. 4l6l. Knownsingle valve meters employ rotary valves and have power index factorsconsiderably in excess of 1.2, the maximum limit permissible under 8.8.No. 4161 part 3 relating to the quality of dry gas meters. Althoughknown twin valve radial motion meters have power index factors of below1.2, the linkage arrangement associated with such valves is extremelycomplicated and cumbersome and in view of the duplication of valves andassociated linkages, construction of such a meter is expensive and timeconsuming. The present invention therefore provides a dry gas meterhaving a valve arrangement which is particularly cheap to manufactureand yet efficient in its operation.

it will be appreciated that the particular embodiment of gas meterillustrated in H68. 115 to 117 will be able to employ a purely circulardiaphragm fixed between the central body 62 and the two pan covers 63and 64. This configuration of the diaphragm is particularly wellillustrated in the side elevational view of FIG. 16 in which the pancover 64 can be seen to be circular and may thus be sealed against thecentral body 62 by means of a circular diaphragm clamped between asealing face of the pan cover 64 and an adjacent sealing face of thecentral body 62.

Thus, when fitting the diaphragm to the meter prior to assembly of thepan cover 64 to the meter body 62, it will be possible to rotate thediaphragm to a position in which there is a minimum amount of crinklingor creasing of the diaphragm before the pan cover is clamped to themeter body thereby ensuring that a good seal is obtained. Such carefulpositioning of the diaphragm is not possible in the constructionillustrated in FlGS. w and lil since there, as shown particularly wellin H6. 11, the diaphragm will be provided with an ear" in order toprovide a continuous seal around the periphery of the passage 4% Thus,the diaphragm must be carefully positioned to seal the passage 46 and nofurther rearrangement is possible when the ear on the diaphragm is inregister with the passage dd, even if severe crinkling or creasing isfound.

A further advantage of the purely circular diaphragm construction isthat there will be no need to manufacture separate left-hand andright-hand diaphragms since the diameters of the two pan covers 63 and64 are the same and thus identically shaped and dimensioned diaphragmsmay be used with each of them.

Although the embodiment of FIGS. 1 to R1 incorporates an arrangement inwhich the index drive shaft or crank spindle is driven independentlyfrom the flag rods and then the valve slide member 7 is driven from theindex drive shaft, it will be seen that the embodiments of H08. E2 to117 illustrate a particularly advantageous construction in which thecrank spindle or index drive shaft is driven from the flag rods by meansof a linkage which includes the valve slide member 7' or 7". Clearly, byincorporating the valve slide 7' or 7" in the linkage between the flagrods and the index drive shaft, a saving in the number of components ofthe meter will have been obtained, thereby simplifying construction andenabling cost of production to be reduced.

We claim:

l. A movable wall gas meter comprising an inlet duct, an outlet duct anda plurality of measuring chambers and a single valve having portscommunicating with the chambers, a valve slide member cooperable withsaid ports, means for subjecting the valve slide member to motionresponsive to movement of the movable wall resulting from the passage ofgas through the meter, and means for constraining the valve slide memberto execute said motion as simultaneous oscillatory motion in both therotational and translational modes in the same plane whereby, during acycle of movement of the valve slide member, each of the ports isconnected to said inlet duct for part of the cycle, to said outlet ductfor a further part of the cycle, and is sealed with respect to inletduct, outlet duct and all other of said ports during the remainder ofsaid cycle.

2. A gas meter as set forth in claim ll, and wherein said valve slidemember comprises a dome having a peripheral seating portion, and whereinsaid valve further includes a valve seating member defining said valveports and over which the valve slide member slides.

3. A gas meter as set forth in claim 2, wherein the valve seating memberincludes exhaust port means and four chamber port means, and the valveslide member and the valve seating member have cooperating slidingsurfaces each provided with inner and outer edges consisting ofrectilinear portions, the exhaust port means having trapezoidallyarranged inner and outer edges, the parallel edges of which lie adjacentto trapezoidal chamber port means and the nonparallel edges of which lieadjacent to respective rectangular chamber port means, said valve slidemember inner edges being hexagonally arranged and valve slide memberouter edges being decagonally arranged so that once during a cycle ofoperation of the valve slide member each rectilinear portion'of theedges of the sliding surface of the valve slide member is in turnsubstantially coincident with and parallel to a rectilinear portion ofthe edges of associated ones of said exhaust port and chamber portmeans.

4. A gas meter as set forth in claim 1, wherein said constraining meansconstrains the valve slide member at two points to execute saidsimultaneous rotational and translational movement,

5. A gas meter as set forth in claim 4, and including an index driveshaft connected to said valve slide member, one of said constrainedpoints being located at the point of connection between said index driveshaft and said valve slide member.

6. A gas meter as set forth in claim ll, and including a meter bodyhaving four measuring chambers and ducts communicating the chambers withtheir respective ports; a casing containing said body, and an indexdrive gear box disposed outside the body but within the casing, saidcasing being exposed to measured exhausting gas.

'7. A gas meter as set forth in claim 1, wherein the chamber ports aredistributed around a centrally disposed exhaust port said inlet ductcommunicating with one side of the valve and said outlet ductcommunicating with said exhaust port and located on the other side ofthe valve.

8. A gas meter as set forth in claim ll, wherein the valve includes avalve seating member in which said ports are disposed, said valveseating member having formed therein a plurality of passages extendingtherethrough, individual passages communicating respective chambers totheir associated parts. 7

9. A gas meter as set forth in claim )1, and including a pair of flagrods each provided with a transversely extending top arm, at least oneof said top arms being connected to said valve slide member.

lit). A gas meter as set forth in claim 9, wherein both said top armsare connected to the valve slide member, said meter including an indexgear box drive shaft driven by the said valve slide member.

ing surrounding the chambers, a pair of flag rods having top arms, oneof the flag rods extending 'sealingly through said casing and the otherflag rod terminating within the space bounded by said casing, and alinkage connecting the two top arms, said linkage including as onemember thereof the valve slide member.

